Rust stains can be difficult, if not impossible, to get out of the carpet. Rust is the result of the reaction of iron with water to create a series of oxides. The resulting stains often require commercial rust removing products such as oxalic acid crystals. Before using any such products read the warning label carefully and be sure you know from what fiber material your carpet is made.
Any rust removal attempts are going to be risky in terms of the welfare of your carpet so be sure to test any methods in an inconspicuous area before applying directly to the carpet.
Salt and lemon juice can sometimes remove rust from fabrics and may be worth exploring as an alternative carpet stain remover. Sprinkle salt on the stain, squeeze enough lemon juice over the stain to cover it, and allow it to soak in the sunlight. Keep in mind that lemon juice is known to lighten colors and could cause your carpet to lighten.
Chlorine bleach is known to set rust stains so even if the stain has marred a white t-shirt do not attempt to remove it with bleach.
Rust can be caused from the legs of your furniture. If you are planning on steam cleaning your carpets, place a protective barrier between the furniture legs and your wet floor such as plastic wrap or wax paper.
“What is rust, What Causes Rust?.” Corrosion Prevention Corrosion Protection Rust Steel and Welding. N.p., n.d. Web. 14 Sept. 2010. <http://www.corrosionist.com/what_is_rust.htm.>
“Carpets Cleaning – General Information.” www.msue.msu.edu: Error Encountered. N.p., n.d. Web. 14 Sept. 2010. http://www.msue.msu.edu/objects/content_revision/download.cfm/revision_id.494693/workspace_id.-4/01500395.html/.